The present invention relates to bearing components and bearings made of bearing steel. More particularly, the present invention relates to bearings including an inner race, outer race positioned coaxially about the inner race and a set of rolling bodies positioned in the space between and in rolling contact with the inner and said outer race.
The discussion that follows contains certain references to various structures and methods. However, nothing that follows should be construed as an admission of prior art.
Many bearing function under poor tribological conditions, which results in bearing wear. The primary method for meeting this problem is to provide proper lubrication. However, for many applications operating at high speeds, high load and elevated temperatures, the available lubricants will not give a satisfactory result.
Attempts have been made to provide rolling bearing components with hard surface coatings, e.g.--carbides and nitrides, such as TiN, TiC, CrN. Although nitrides and carbides have high hardness and a good resistance to abrasive wear, they also pose a problem. Because their friction coefficients are rather high, which in combination with the high hardness, leads to excessive abrasive wear on components in rolling or sliding contact with these coated elements.
Moreover, sufficient adhesion between coatings of this type and the substrate are not obtained unless the application temperature of the coating is high (over 400.degree. C.). At these temperatures, the comparatively low alloyed bearing steels will be subjected to excessive softening and dimensional changes.
Therefore such coating materials do not give a satisfactorily result.
Coatings of diamond-like carbon (DLC) have been used to coat sliding bearing components. The adhesion of this material against the underlying bearing steel material is sufficient for sliding bearing applications, but as a result of the much higher contact stresses in rolling bearings, in combination with the fact that DLC is not thermally stable and have inferior elastic properties, it has proven itself to have insufficient adhesion for most rolling applications as the DLC coating will flake off.
Some have sought to apply DLC coatings to rolling bearings by providing specific interlayers. However, the limited elastic properties of the DLC coating have meant a limited usefulness in such applications.
One objective of the present invention is to provide a well functioning rolling bearing component made of bearing steel. The component may one or more of an inner race, an outer race positioned coaxially about the inner race and a set of rolling bodies positioned in the annular space between and in rolling contact with the inner and outer races, and which has an increased life also under severe operation conditions with poor lubrication.